Why file does not including into controller?

I have installed the package from composer I am trying to include file from vendor folder into controller but it does not including.

Here is what I am trying

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use src\Coinpayments;
use src\keys;
class CoinController extends Controller
{

    public function DoIt(){
            $cps = new CoinPaymentsAPI();
        }
}

And this is in composer.json

 "require": {
        "php": "^7.1.3",
        "coinpaymentsnet/coinpayments-php": "^1.0",
        "fideloper/proxy": "^4.0",
        "laravel/framework": "5.8.*",
        "laravel/tinker": "^1.0"
    },

In the result I am getting following error which is

Class 'App\Http\Controllers\CoinPaymentsAPI' not found

Can someone kindly guide how can I resolve it I will be much thankful

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